"hi sir i hop you are fine sir my question about graptolite that what type of fossil it is?? and is graptolite has further divisions??? please also tell weather what type of it are present in pakistan and in which areas of pakisatn???? i shall b very thank full to you"
Graptolites (formally known by their scientific name Graptolithina) are extinct marine creatures that formed twig-like or net-like colonies composed of one or more branches. These colonies mostly floated freely in the sea but some may have been attached to the sea floor. Because of their branching form they may have superficially resembled seaweed but they were in fact animals. Each colony was made up of a large number of individual microscopic animals that lived in a series of tiny cup-like structures arranged along the branches of the colony. The individual animals were all joined together by a type of nerve cord.
Where are graptolites found?
Graptolites first appeared in the Cambrian Period, 545–490 million years ago (mya), and evolved rapidly during the following Ordovician Period (490–434 mya) when the greatest variety of different forms lived. They suffered a major decline in the Silurian (434–410 mya) and only a few forms lasted into the Devonian. They finally became extinct during the Carboniferous Period, about 315 my ago.
Graptolites are a group of colonial hemichordates, long considered extinct, although recent systematic work has suggested the group is equivalent to modern pterobranchs (Mitchell et al., 2010). Although the most primitive members of the group are benthic and attached to the sea floor, one lineage of graptolites became planktonic around ~490 million years (MY), the base of the Ordovician period. We refer to any members of this lineage as graptoloids, also known as the planktic graptolites or the Eugraptoloidea (as defined by Maletz et al., 2008). Graptoloids underwent rapid diversification in the later Ordovician, suffered immense losses during the Hirnantian mass extinction and radiated again during the Silurian period. The last few lineages of graptoloids finally died out around ~418 MY, in the early Devonian. During their relatively brief ~80 MY history, the graptoloids experienced extremely rapid taxonomic turnover, with over two thousand species observed in the fossil record.
In terms of their construction and physiology, graptoloid colonies were essentially a ‘floating bee hive’. Zooids, probably very similar to the small suspension-feeding zooids of Rhabdopleura, were apparently very motile. The preserved portion of graptolite colonies is a protein-rich material secreted and molded into desired components by each zooid. The most basic component was a repeated half-ring to form tubes; this is the same construction seen in some pterobranchs colonies. Thus, graptolite colonies are constructed objects, like bee hives, termite nests, packrat middens or bird nests.
Further reading as follows;
In Pakistan graptolites present in Northern part of Pakistan (karakorum and Hindukush ranges) where Paleozoic rocks are exposed
Read the following